Device for starting and feeding electric discharge tubes under low pressure



DEVICE FOR STARTING AND FEEDING ELECTRIC DISCHARGE Nov. 10, 1942.LECORGUILLIER 2,301,891

TUBES UNDER LOW PRESSURE Filed July 18, 1939 Patented Nov. 10, 1942nsvrcs roa srsnrmo AND rssnmo use. 'rnro mscnsncs 'russs rmnsn LOWreassess Jean Lecorguillier, Suresnes, France, assignor to SocieteAnonyme pour les Applications de UNITED STATES PATENT, OFFICElElectricite a; des Gas Rares-Etablissements Claude-Pal & Silva, Paris,France Application July 18, 1939, Serial N0. 285,111 In switlel'lantlMarch 29, 1939 Claims. (or. 176-124) There are known so-called constantvoltageconstant current circuits which are formed of combinations oftuned inductance and capacitance elements and which, when they aresupplied from a constant voltage source at their in systems, hereinaftercalled feed systemsl'to the operation of low voltage electric dischargetubes.

, These tubes are fitted with therm'o-emitting electrodes heated by thedischarge from a constant voltage alternating source, for instance oneof the usual low tension sources (110 or 220 volts). Only those voltagesare permitted in a receiving circuit which do not exceed the limitauthorized by the regulations for usual distributions. Furthermore, thedevice according to the invention, which does not work with a uniformintensity, occupies a minimum of space, consumes very little energy, andhas ahigh power factor, without reducing the life of the tube employed.

The accompanying drawing shows merely by way of example an embodiment ofthe invention, comprising a constant voltage-constant current circuit ofthe Wheatstone bridge type. 1

In this drawing, A and B designate the terminals of the constant voltagesource of distribution. C and liartlieterminals of the receivingcircuit. and 3 are the inductorsfand 2 and l are thecapacitors of thefeed system, these elements being respectivelitequal to each other., I

' 'isthe stabilizing inductanfioeilln s ries with the luminescentdischarge 0 The fuse'is-findl catedat I.

According to the present invention, when th tube is connectedin serieswith an inductance *coil in the receiving circuit, the followingconditions are simultaneously complied with:

(a) The stabilizing impedance has such a value that it would secure thestability of the tube when the tube with its impedance is supplied withaconstant voltage, this voltage actually being lower than twice thevoltage across the tube under working conditions:

three times the constant input voltage and at most equal to the maximumvoltage permitted by the regulations concerning low voltagev systems(for instance 250 volts in France);

(0) The circuit leading .to the terminals of the source of distributionincludes a device for automatically cutting oii the current (fuse orcircuit-breaking relay) adjusted to operate at the open circuit current.

The stabilizing impedance such as deilned above prevents any rapi ddeterioration of the electrodes during the starting oi the tube and itsoperation. Its value is very much higher than it would be advantageousto use with a tube having cold electrodes. It isimportant to note thatthevalueoiithisim pedance is indepeuilent of the supply circuit and ofthevalue of the elements thereof, although these elements intervene forthe stabiligation of the tube.

Stabilization with the constant voltage supply considered at a. above isto be considered as secured when a change of current in the tube between and 18% corresponds to an incidental change of 16% in the normalsupply voltage. In

the present invention, owing to the influence oi the feed systemelements, the stabilization obtained for the'entire device will ofcourse be still better.

ated by the provision oi a current cutting means,

which allows these elements tobe dimensioned only-as far as necessaryfor the flow of a curthe tube starting voltage, but it is lower refit.equal to that which passes therethrough whenthetube is being started,during the period for bringing itinto normal oger ating qondifl It hasbeen founit tQatthe starting tim,"desplte' the low'overvoltage employedfor this starting, is

sumciently short to .allow a material reduction inthe sizeof the system.'IhesLeis very small compared with that which would behecessu'y in theabsence of the circuit-breaking meansfif the elements had been chosen insuch manner as to support the current flowing therethrough in case thewas brought out of service.

The automatic circuit breaking means may be a delayed action fuse,adjusted to operate after the elapsing of the time required for startingthe tube, provided the tube has not actuallybeen started. This fusecomprises for instance an electric heating coil, which may be made of ametal the resistance of which increases considerably when thetemperature rises, surrounding a mass of fusible alloy, forinstance-Lipowitz alloy (26.3% of lead, 13.3% of tin, 50% of bismuth, ofcadmium, melting point 70 C.) with which it is in series. The fuse maybe terminated by a spring under tension with one of its ends embedded inthe fusible mass. But it has been found that in most cases it issufficient to employ an automatic current circuit breaking means actingwithout delay, for instance an ordinary fuse. The same is true when theinterval between the open circuit current and the starting current isrendered sumcient to permit the starting of the tube without operatingthe circuit breaking means. The starting input current can be reducedwith respect to the open circuit current in a suitably proportionedplant (as to the voltage delivered by the supply network, the startingvoltage and the characteristics of the tube). larger than the startingcurrent as the following two ratios are larger, firstthe ratio of thestarting voltage to the working voltage at the output, and second-theratio of the open circuit current a to the working current at the input.The inductance coil iif'seri'es with the tubeis preferably proportionedso that the induction therein developed by the starting current issufiiciently low to avoid saturation by the temporary current peaks,such as occur duringtlre, starting. This induction is chosen, forinstance, togrange from 66% to i590 Gauss. v

What I claim is:

l. A circuit arrangement for supplying an electric discharge lamp withcurrent from a low voltage source comprising, a ballast impedance in Mseries with said lamp, the value of said impedance The open circuitcurrent is in fact inn the current in being such that an incidentalchange,oi-l0%"in the voltage applied rto thrrlamfland its impedance willcause a change of less than 30% in the current' in the lamp when saidvoltage is lower than approximately twice the voltage across the latopen circuit current of the net lamp under working conditions, a networkof the constant voltage-constant current type including two sets ofinductances and capacitances, each of said sets comprisingone-inductance and one capacitance connected across said discharge tubeand its impedance, the inductances and capacitances being respectivelyequal to each other, said network having its input and output sidesconnected to said low voltage source and said circuit respectively andbeing so proportioned as to yield at its output side an open circuitvoltage lower than a predetermined value below approximately three timesthe constant input voltage and a working output as required by saidcircuit, a circuit breaker in the input connections of said networkwhich will withstand and maintain the circuit closed during the,startingof the tube but which will break the circuit M work; the elements ofthecircuit being of smaller size than that which would be required under asteady open circuit operation of the network.

, 2. A circuit'arrafigement for supplying an electric disch arge'lampwith current from a low voltage source comprising, a ballast inductancein series with the lamp, said ballast inductance being so proportionedas not to be saturated by the current peaks occurringsin the networkduring the starting of the lamp and having such a value that anincidental change of 10% in the voltage applied to the lamp and itsimpedance will cause a change of less than 30%. in the current in thelamp when said voltage is approximately lower than twice the voltageacross the lamp under working conditions, a network of the constantvoltage-constant current type including two sets of inductancesand'capacitances, each of said sets comprising one inductance and onecapacitance connected across said discharge tube and its impedance, theinductances and capacitances being respectively equal to each other,said network having its input and output sides connected to said lowvoltage sourceand said circuit respectively and being so proportioned asto yield at its output side an open circuit voltage lower than apredetermined value below approximately three times the constant inputvoltage and a-working output as required by said circuit, a circuitbreakerin the input connections of said network which will withstand theinput current and maintain the circuit closed during the starting of thetube but which will break the circuit at open circuit current of thenetwork; the elements of the circuit being of smaller size than thatwhich would be required under a steady open circuit operation of thenetwork. v 3. A circuit arrangement for supplying an electric dischargelamp with current from a low voltage source comprising, a ballastimpedance in series with said lamp, the value of said impedance beingsuch that an incidental change of 10% in the voltage applied to the lampand its impedance willcauseachangeof less than 30% approximately lowerthan twice the voltage across the lamp under working conditions, anetwork of the constant voltage-constant current type including two setsof inductafices and capacitances, each of said sets comprising oneinductance and one capacitance connected across said discharge tube andits impedance, the inductances and capacitances being respectively equalto each other, said network having its input and output sidesconnected-to said low voltage source and said circuit respectively andbeing so proportioned as to yield at its output side an open circuitvoltage lower than a predetermined value below approximately three timesthe constant input voltage and a working output as required by saidcircuit, a circuit breaker of the delayed action type in the inputconnections of said network which will delay over the time required forstarting the tube and maintain the circuit closed but will break thecircuit at the network; the elements of the circuit being of smallersize than that which would be required under a steady open circuitoperation of the the input; w-age source comprising, a ballast impedancein series with said lamp, the value of said impedance being such that anincidental change of 10% in the voltage applied to the lamp and itsimpedance will cause a change of less than 30% in the current in thelamp when said voltage is approximately lower than twice the voltageacross the lamp under working conditions, a network of the constantvoltage-constant-current type including two sets of inductances'andcapacitances, each of said sets comprising one inductance and one catthelamp whenlsaid voltage is open .circuitcurre of pacitance connectedacross said discharge tube and its impedance, the inductances andcapacitances being respectively equal to each other, said network havingits input and output sides connected to said low voltage source and saidcircult respectively and being so proportioned as to yield at its outputside an open circuit voltage lower than a predetermined value. belowapproximately three times the constant input voltage and a workingoutput as required by said circuit, and which,-during the starting ofthe lamp, will take an input current substantially lower than the opencircuit input current, a circuit breaker in the input connections ofsaid network which will withstand the input current and maintain thecircuit closed during the starting of the tube but which will break thecircuit at open circuit current of the network; the elements of thecircuit being of smaller size than that which would be required under asteady open circuit operation of the network.

5. A circuit arrangement for supplying an electric discharge lamp withcurrent from a low voltage source comprising a ballast impedance inseries with said lamp, the value of said impedance being such that anincidentalchange of 10% in the voltage applied to the lamp and itsimpedance will cause a change of less than 30% in the current in thelamp when said voltage is approximately lower than twice the voltageacross the lamp underworking'conditions, a network of the constantvoltage-constant current type including two sets of inductances andcapacitances, each of said sets comprising one inductance and onecapacitance connected across said discharge tube and its impedance, theinductances and capacitances being respectively equal to each other,said network having its input connected to said low voltage source andits output connected to the lamp and its impedance and being soproportioned as to yield at its output side an open. circuit voltagelower than a I predetermined value below-approximately three times theconstant input voltage and yielding a working voltage as required bysaid lamp, an automatic circuit breakerof the delayed action type in theinput connections of said network, said circuit breaker being adjustedto operateupon failure of the lamp to start; after atime intervalnormally required to start the lamp, the elements of the circuit beingof-smaller size than that which would be required under a steady opencircuit operation of the network.

